Pumps and PumpingPumps and Pumpingin Irrigation applicationsin Irrigation applications

Basic Pump TheoryBasic Pump Theory

John Starke: Irri – Gator ProductsJohn Starke: Irri – Gator Products

What do Pumps pump?What do Pumps pump?

Slurry - Liquids - Gases - etcSlurry - Liquids - Gases - etc

oilsoils petroleumpetroleum waterwater fertiliserfertiliser

liquid foodsliquid foods seweragesewerage airair etc-etcetc-etc

What type of pumps are there? What type of pumps are there?

Centrifugal – single or multi stageCentrifugal – single or multi stage Positive displacement Positive displacement RotaryRotary PeristalticPeristaltic Axial flowAxial flow

TurbineTurbine VacuumVacuum PistonPiston etc-etcetc-etc

Pumps Commonly found in Pumps Commonly found in IrrigationIrrigation

Centrifugal = used for pumping water Centrifugal = used for pumping water Positive displacement rubber screw (Mono) =Positive displacement rubber screw (Mono) = lower volume high pressure = pumping waterlower volume high pressure = pumping water Piston type very low volume – precise =Piston type very low volume – precise = fertiliser injectionfertiliser injection Turbine = pumping water Turbine = pumping water Submersible – multistage – low to med volume +Submersible – multistage – low to med volume +

higher pressures = boreholehigher pressures = borehole Submersible – single stage – high volume + low Submersible – single stage – high volume + low

pressure = dewatering pressure = dewatering

Concentrate on Centrifugal Concentrate on Centrifugal Pumps for pumping Irrigation Pumps for pumping Irrigation

water.water.

What is a Centrifuge or What is a Centrifuge or

Centrifugal force?Centrifugal force?

A A Centrifuge is: is: a piece of equipment - a piece of equipment - generally driven by a motor - generally driven by a motor - that puts an object in that puts an object in rotation around a fixed axisapplying a force -applying a force -perpendicular to the axis.perpendicular to the axis.

Centrifugal & Centripetal Forces

Centrifugal PumpsCentrifugal Pumps A centrifugal pump is one of the simplest types of pump A centrifugal pump is one of the simplest types of pump

that uses centrifugal force to move fluid into a pipe. that uses centrifugal force to move fluid into a pipe.

The basic purpose of the pump is to convert energy of an The basic purpose of the pump is to convert energy of an electric motor , or engine into velocity or kinetic energy and , or engine into velocity or kinetic energy and then into pressure of a fluid that is being pumped.then into pressure of a fluid that is being pumped.

Centrifugal pumps are the most commonly used pump and Centrifugal pumps are the most commonly used pump and their operating cost is low compared to other pumps. their operating cost is low compared to other pumps.

They are reputed for high reliability and ensure smooth They are reputed for high reliability and ensure smooth operation.operation.

Centrifugal PumpCentrifugal PumpDelivery Flange

Backing Plate

Bearings

Gland Packing

Volute Casing

Impeller

Suction Flange

Shaft

Pedestal

Pump TerminologyPump Terminology

Duty PointDuty Point = a certain flow of water at a certain = a certain flow of water at a certain pressure to fulfil the system requirement – pressure to fulfil the system requirement – constant or varyingconstant or varying

Pump Efficiency Pump Efficiency = how effectively the pump = how effectively the pump converts the input energy into water pressureconverts the input energy into water pressure

Rotational SpeedRotational Speed = Speed at which the Impeller = Speed at which the Impeller turnsturns

Positive SuctionPositive Suction = The water flows into pump on = The water flows into pump on its own e.g. below dam wallits own e.g. below dam wall

Pump TerminologyPump Terminology

Negative Suction Negative Suction = The pump has to “lift” = The pump has to “lift” the water from a source lower than itself the water from a source lower than itself e.g. rivere.g. river

NPSH NPSH = refers to the maximum “lift” = refers to the maximum “lift” capability a pump has to extract water capability a pump has to extract water from a source lower than itselffrom a source lower than itself

Cavitation Cavitation = Noise in the Volute Casing of = Noise in the Volute Casing of a Pump due to the presence of a Pump due to the presence of undesirable air particles implodingundesirable air particles imploding

Pump Identification & Pump CurvesPump Identification & Pump Curves

•Pump Manufacturer – e.g. KSB; Rapid Allweiller; GrundfosPump Manufacturer – e.g. KSB; Rapid Allweiller; Grundfos

•Pump Type - Single Stage - 65/250; 80/40; 150/315 etcPump Type - Single Stage - 65/250; 80/40; 150/315 etc Multistage - 80/40 – 2 stage; WKLN 65/4 etcMultistage - 80/40 – 2 stage; WKLN 65/4 etc

•Impeller Size – e.g. 250mm; 185mmImpeller Size – e.g. 250mm; 185mm

•Motor Size – kilowatts or horsepowerMotor Size – kilowatts or horsepower

•Speed of Motor – 2 / 4 Pole or 29?? / 14?? RPMSpeed of Motor – 2 / 4 Pole or 29?? / 14?? RPM

•Efficiency of motor – ?Efficiency of motor – ?

•Power factor of motor – cos ?Power factor of motor – cos ?

Typical Motor Identification PlateTypical Motor Identification Plate

Typical Pump Identification PlateTypical Pump Identification Plate

What is a Pump Curve?What is a Pump Curve?

Pressure / Head DevelopedPressure / Head Developed

Flow rate of liquidFlow rate of liquid

Power consumed @ Duty point and Non overloadPower consumed @ Duty point and Non overload

NPSH requiredNPSH required

Efficiency of pumpEfficiency of pump

This is the characteristics of the pump when This is the characteristics of the pump when operating at a specific speed and giving the operating at a specific speed and giving the

following info:following info:

65 / 250 Centrifugal Pump65 / 250 Centrifugal PumpH

ead

in

Met

res

Flow rate in m³ per hour 120m^3/hour

82m

120

120m³/hr@82m

80m³/hr@54m

17kW Power

37kW Power

80

82 meters head

71% efficiency

Nett pump suction head required is 4,6m

Motor size required for non overload is 45 kW

120 m^3/hr

Laws of AffinityLaws of Affinity

The affinity laws express the mathematicalThe affinity laws express the mathematical

relationship between the several variables relationship between the several variables

involved in pump performance. involved in pump performance.

They apply to all types of centrifugal and They apply to all types of centrifugal and

axial flow pumps. axial flow pumps.

They are as follows:They are as follows:

Volume CapacityVolume Capacity

The volume capacity of a centrifugal pump can The volume capacity of a centrifugal pump can be expressed as:be expressed as:

q = (n1 / n2) x (d1 / d2) q = (n1 / n2) x (d1 / d2)               

Where:Where:

qq = volume flow capacity (m= volume flow capacity (m³³ / hour) / hour) n = wheel velocity - revolution per minute - (rpm)n = wheel velocity - revolution per minute - (rpm) d = wheel diameter – (mm)d = wheel diameter – (mm)

Head or PressureHead or Pressure

The head or pressure of a centrifugal pump can The head or pressure of a centrifugal pump can be expressed as:be expressed as:

h = (n1 / n2)h = (n1 / n2)²² x x (d1 / d2)(d1 / d2)²²              

Where:Where:

h = h = headhead or pressure  (metres) or pressure  (metres)

PowerPower

The power consumption of a centrifugal pump The power consumption of a centrifugal pump can be expressed as:can be expressed as:

P = (n1 / n2)P = (n1 / n2)³³ x x (d1 / d2)(d1 / d2)³³              

Where:Where:

PP = power (kilowatt)= power (kilowatt)

Changing the Impeller SpeedChanging the Impeller Speed If the If the Impeller diameter is Impeller diameter is constantconstant - change in - change in

Impeller speed can simplify the affinity laws to:Impeller speed can simplify the affinity laws to:

Volume CapacityVolume Capacity

q1 / q2 = (n1 / n2)q1 / q2 = (n1 / n2)

                 Head or PressureHead or Pressure

dp1 / dp2 = (n1 / n2)dp1 / dp2 = (n1 / n2)²²

                     PowerPower

p1 / p2 = (n1 / n2)p1 / p2 = (n1 / n2)³³                

If the speed of a pump is increased with If the speed of a pump is increased with 10% then:10% then:

the volume flow increases with the volume flow increases with 10%10% the head increases with the head increases with 21%21% the power increases with the power increases with 33 %33 %

If we want to increase the volume of an If we want to increase the volume of an existing system with existing system with 10%10% we have to we have to increase the power by increase the power by 33%33%..

How NOT to do it !!How NOT to do it !!

How many of these How many of these do we see ? !!do we see ? !!

Pump House or Pump House or Store Room?Store Room?

Time for an Upgrade ??!!Time for an Upgrade ??!!

Rather do THIS !!!Rather do THIS !!!

Or This !Or This !

Sell some of these!!!!Sell some of these!!!!

ThanksThanks